Any way to make a MicroQuiet 4k quiet?

[tap4154]

Well I found the best way to lower the DBs on this generator, download a different app. With my old app I get 66 at the same time the new app says about 56.

That aside, I did put that Dynamat type sound proofing along the back and left side of the generator housing, and some underneath and on the door of the cabinet. I honestly don't know if it helped or not, it may have dropped 1 DB.

So I tried something else, I loosened the bolts that mount the generator to the cantilever arms, jacked up each side of the generator one at a time, and inserted some heavy quarter inch rubber I cut from a rubber tie-down between the arm and the generator. Then I remounted the bolts using a larger washer and 2 neoprene washers to hopefully help isolate it from the metal. Again, I don't know if it helps or not, but with the old app I'm still getting a steady 65 to 66 and the new app is 55 to 56.

At least I got the new exhaust hangers on, and overall it is quieter than it was. Actually I'm taking the DB ratings right inside the entry door which is toward the front of the motorhome near the generator, when I'm back in the bedroom I'm only getting about 56 from my old app and 46 on the new one.

[jjrbus]

Quieting one of these is like trying to play fetch with a rabid dog. They make and sell vibration isolating mounts. The cheaper they are the harder the rubber, the harder the rubber the less they dampen vibration. If they do not mention rubber hardness they are hard! Durometer or shore hardness??


https://www.amazon.com/Mechanical-Vi...&node=16413771


https://www.essentracomponents.com/e...hoC-c8QAvD_BwE

[Xmcdog]

Maybe some of this may help?

https://lizardskin.com/

Just a thought. I've never used it but maybe.......

[gatorb8]

If you can meet your needs with 2800 watts and don’t mind spending the kids inheritance, chuck that 4000 and install the new Onan QG2800i inverter generator, it’s super quiet. Or, maybe wait for the 4000 inverter generator that Onan is probably developing.

whenever I show folks my QG2800i they are amazed.

other than that, the best thing I found for outside generator noise on previous generators was carpet on the ground underneath the generator, the added muffler did very little, maybe a db or two

vibration noise was difficult to reduce as every installation is different

[tap4154]

Originally Posted by jjrbus

Quieting one of these is like trying to play fetch with a rabid dog. They make and sell vibration isolating mounts. The cheaper they are the harder the rubber, the harder the rubber the less they dampen vibration. If they do not mention rubber hardness they are hard! Durometer or shore hardness??


https://www.amazon.com/Mechanical-Vi...&node=16413771


https://www.essentracomponents.com/e...hoC-c8QAvD_BwE

Good suggestions, and I also had searched those on Amazon. The ones with the studs in them I don't think would work. I need them with the hole in it so I can use the existing bolts. Some of those I've read seem to be very soft and they might be too soft for this generator. Better for lighter-weight objects.

Yesterday I found some Dorman shock absorber bushings at an auto parts store, they only had four of them. I put those underneath, and today I'm going to see if I can find four more and put them above, between the frame and the generator bottom. Right now you can see I just have some cut chunks of hard rubber between the generator and the frame, but underneath is shock absorber rubber bushing.

[tap4154]

I got one corner fixed, have a shock absorber bushing on top and bottom of the cantilever frame. Just got to get four more and finish the other three corners.

[tap4154]

Got the bushings mounted on all four corners, and also used some of that sound material to sort of close off the left and right side in the front of the compartment. So now it's closed off partially on the sides and on the top by the foam roller material I put in. I have no idea how many DB's it is because every app I download reads differently, but it is substantially better. Also less vibration in the floor.

Think I'll call it a day at that, and I've done nothing that obstructs the inlet air flow or the cooling exhaust flow.

[Phil G.]

It's probably too late for some reading this discussion thread, but if one really wants to do it right (even if some slight bracket redesign/redrilling is required), these are the kind and quality of mounts to use for an Onan generator in an RV:
https://www.avproductsinc.com/mobile...fe-mounts.html

[tap4154]

Originally Posted by Phil G.

It's probably too late for some reading this discussion thread, but if one really wants to do it right (even if some slight bracket redesign/redrilling is required), these are the kind and quality of mounts to use for an Onan generator in an RV:
https://www.avproductsinc.com/mobile...fe-mounts.html

You're absolutely right, that would be the best way to go, it's just way more work than I wanted to get involved in. I do think my simple solution did help though. And because most of the noise is coming from the intake and cooling exhaust, I don't think all the extra work would have been worth it.

[CharlesinGA]

Did you put metal spacers thru the shock bushings so the bolts could be torqued? Otherwise you are just squeezing the rubber some and hoping the bolts will not back out. In theory you would use shoulder bolts that the shoulder seats on the bottom pan of the generator and allows the bolt to tighten up.

If you don't do something you can expect the bolts to work loose. At least drill the heads and safety wire them to the brackets.

Charles

[CharlesinGA]

Originally Posted by tap4154

Thank you for all the information Charles. Yes I already ordered a couple Onan hangers, actually they're arriving today..

That resonator made quite a difference on yours. Mine has the muffler up in the right side, then the pipe comes down and runs forward, then out, so it is a fairly long exhaust pipe. But really, I don't hear that much noise from the exhaust itself, I just hear more mechanical noise. As you said, a lot of it is coming out of the cooling exhaust area.

Also, to put a resonator underneath by cutting a section of pipe out, I'd need to weld it and I don't have that capability. I don't know if I'd want to trust just using clamps on an exhaust pipe underneath the motorhome.

I agree about the ground noise, I tried some folded up cardboard underneath the generator and it does cut down the sound to a certain degree. It's parked on brick in the backyard so that amplifies the noise quite a bit.

...........Snip............

By the way I love that second video, very informative. I gave you a thumbs up.

Yes, the 2500/2800 has a muffler inside also, that the exhaust connects to. As my exhaust was cracked at the 90 from a messed up mounting of the pipe hanger, it was cracked and the guy at a local independent muffler shop suggested just welding the cracks as the pipe was solid. So we welded the cracks and welded in the resonator. I agree, I would not want a clamped in resonator running under my trailer or MH. The guy didn't get the resonator too centered putting it too far into the pipe on one end and barely in on the other, but its welded so it isn't going anywhere. It eliminates a 'poot-poot" sound the exhaust had and the rest of the noise is mechanical, tappets clicking and mechanical engine noises. Inside the sound is about the same, its outside that made the difference.

Increasing the choke spring allows it to start right off every time now, no grinding and trying several times. Hit the button and it fires right off.

As I noted, I found one YT video where he installed a resonator on a 4000 and it didn't make any real difference.

Thanks for the thumbs up on the video.

Charles

[tap4154]

Originally Posted by CharlesinGA

Did you put metal spacers thru the shock bushings so the bolts could be torqued? Otherwise you are just squeezing the rubber some and hoping the bolts will not back out. In theory you would use shoulder bolts that the shoulder seats on the bottom pan of the generator and allows the bolt to tighten up.

If you don't do something you can expect the bolts to work loose. At least drill the heads and safety wire them to the brackets.

Charles

I figured 'ld just check them occasionally and snug them up. I don't really want to drill out the holes in the cantilever arm much because there's not a whole lot of room to drill them out. In fact the factory drilled out and elongated one because apparently the holes was weren't lining up, and it left not much metal to the edge. Also might remove the bolts and put a little Loctite threadlocker on the threads.

But I'll think about it, shoulder bolts are good idea as well. I just was trying to avoid any metal to metal contact. Right now I don't think the bolts are making much contact with the cantilever arms, if I use shoulder bolts I'm going to have to really drill out the hole quite a bit to make sure there's no metal to metal contact.

[jjrbus]

The isolators work much better if attached to something solid, such as a concrete floor, impractical for us. I used the softest I could find in my size which IIRC was a 38 durometer. Time will tell if they will hold up, they do reduce noise transmission noticeably. Would have been impracticable to check db.



One tinkerer made a rubber cradle to hang his generator in, claimed great results.

[Phil G.]

As others have mentioned, most of the noise from built-in Onan RV generators is sound bouncing off the ground under it when camping.

I've seen large motorhomes with those black rubber slitted skirts across the back - to help keep dust/dirt off the rear outside coach wall and any toad they might be towing.

I wonder if one of those rubber skirts couldn't be permanently mounted hanging down under an Onan generator - creating a kindof closed-in rectangular shaped skirt wall right under the Onan? This would block a lot of the sound bouncing off the ground when camped with it running, would not block any airflow around the bottom of the generator with it running, and ... could be left in place for years ... since the thin rubber fingers hanging down could hardly be damaged from anything on the road surface such as curbs, rocks, etc. when moving. Fuel mileage from this rubber skirt's fingers hanging down in the air stream should not be significantly affected, either.